Azure Functions Tutorial

1. Introduction to Azure Functions

Welcome to the Azure Functions tutorial! Azure Functions is a serverless compute service that enables you to run code on-demand without explicitly provisioning or managing infrastructure. It's a powerful way to build event-driven applications and microservices that scale automatically.

In this tutorial, you will learn how to:

• Set up your local development environment.
• Create and run your first Azure Function.
• Understand core concepts like triggers and bindings.
• Deploy your function to Azure.

2. Prerequisites

Before you begin, ensure you have the following installed:

• Azure Subscription: You'll need an active Azure account to deploy your functions. If you don't have one, you can sign up for a free trial.
• Azure Functions Core Tools: This is a command-line tool that lets you develop and test Azure Functions locally. Install it via npm:

  npm install -g azure-functions-core-tools@4 --unsafe-perm true

• Development Environment:
  • Visual Studio Code (Recommended): With the Azure Functions extension installed.
  • Or, your preferred IDE with support for your chosen programming language (e.g., Visual Studio, JetBrains Rider).
• Programming Language SDK: Depending on your choice, you'll need the SDK for languages like C#, Node.js, Python, PowerShell, or Java.

3. Setting up your Environment

Let's set up your local workspace. We'll use Visual Studio Code for this example.

1. Open Visual Studio Code.
2. Open the Command Palette (Ctrl+Shift+P or Cmd+Shift+P).
3. Type `Azure Functions: Create New Project...` and select it.
4. Choose a folder for your project.
5. Select your preferred language (e.g., JavaScript).
6. Choose a template for your first function (we'll create one in the next step, so you can choose `Skip for now` or a basic template).

4. Creating your First Azure Function

Now, let's create a simple HTTP-triggered function. This is a common starting point.

1. In VS Code, open the Command Palette (Ctrl+Shift+P or Cmd+Shift+P).
2. Type `Azure Functions: Create Function...` and select it.
3. Choose your project folder if prompted.
4. Select the trigger type: `HTTP trigger`.
5. Provide a name for your function (e.g., `HttpExample`).
6. Choose an authorization level. For local testing, `Anonymous` is usually fine.

This will create a new folder for your function (e.g., `HttpExample`) with files like index.js (or __init__.py for Python, etc.) and function.json.

Here's an example of a basic JavaScript HTTP trigger:

// HttpExample/index.js
module.exports = async function (context, req) {
    context.log('JavaScript HTTP trigger function processed a request.');

    const name = (req.query.name || (req.body && req.body.name));
    const responseMessage = name
        ? "Hello, " + name + ". This HTTP triggered function executed successfully!"
        : "This HTTP triggered function executed successfully. Pass a name in the query string or in the request body for a personalized response.";

    context.res = {
        // status: 200, /* Defaults to 200 */
        body: responseMessage
    };
};

And its configuration in function.json:

// HttpExample/function.json
{
  "bindings": [
    {
      "authLevel": "anonymous",
      "type": "httpTrigger",
      "direction": "in",
      "name": "req",
      "methods": [
        "get",
        "post"
      ]
    },
    {
      "type": "http",
      "direction": "out",
      "name": "res"
    }
  ]
}

5. Understanding Triggers and Bindings

Triggers and bindings are the core concepts that make Azure Functions powerful and easy to use. They abstract away the complexities of interacting with other Azure services and external event sources.

Triggers

A trigger defines how a function is invoked. When a trigger event occurs, the Azure Functions runtime executes your function. Common triggers include:

• HTTP Trigger: Invokes your function when an HTTP request is received.
• Timer Trigger: Invokes your function on a schedule (like cron jobs).
• Blob Trigger: Invokes your function when a new or updated blob is detected in Azure Blob Storage.
• Queue Trigger: Invokes your function when a new message arrives in an Azure Storage Queue.
• Event Grid Trigger: Invokes your function in response to events from Azure Event Grid.

Bindings

Bindings allow you to connect to other Azure services (input and output) without writing custom integration code. They are declared in the function.json file.

• Input Bindings: Provide data to your function. For example, you can bind to a document in Cosmos DB or a blob in storage.
• Output Bindings: Allow your function to write data to other services. For example, you can write a message to a Service Bus queue or save a blob.

6. Deploying to Azure

Once you've developed and tested your function locally, it's time to deploy it to Azure.

1. Sign in to Azure: In VS Code, open the Command Palette and run `Azure Functions: Sign in to Azure...`.
2. Create Azure Resources: You'll need an Azure Function App resource in Azure. You can create this directly from VS Code.
   • Open the Command Palette and select `Azure Functions: Create Function App in Azure...`.
   • Follow the prompts to select a subscription, give your function app a globally unique name, choose a runtime stack, and select a region.
3. Deploy: After creating the Function App resource, you can deploy your local project to it.
   • Right-click on your project folder in the VS Code explorer.
   • Select `Deploy to Function App...`.
   • Choose the Azure Function App you just created.

After deployment, you can access your function's endpoint via the URL provided in the Azure portal or VS Code output.

7. Next Steps

Congratulations on creating and deploying your first Azure Function! Here are some ideas for further exploration:

• Explore different triggers and bindings: Try out Timer, Blob, or Queue triggers.
• Learn about durable functions: For building stateful serverless workflows.
• Implement error handling and logging: Make your functions robust.
• Configure application settings: Manage environment-specific configurations.
• Monitor your functions: Use Application Insights for detailed monitoring.

Continue your serverless journey with Azure Functions!